/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.varia;

import org.apache.log4j.spi.ErrorHandler;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.Appender;
import org.apache.log4j.Logger;
import org.apache.log4j.helpers.LogLog;
import java.util.Vector;

/**
 * 
 * The <code>FallbackErrorHandler</code> implements the ErrorHandler interface
 * such that a secondary appender may be specified. This secondary appender
 * takes over if the primary appender fails for whatever reason.
 * 
 * <p>
 * The error message is printed on <code>System.err</code>, and logged in the
 * new secondary appender.
 * 
 * @author Ceki G&uuml;c&uuml;
 * */
public class FallbackErrorHandler implements ErrorHandler {

	Appender backup;
	Appender primary;
	Vector loggers;

	public FallbackErrorHandler() {
	}

	/**
	 * <em>Adds</em> the logger passed as parameter to the list of loggers that
	 * we need to search for in case of appender failure.
	 */
	public void setLogger(Logger logger) {
		LogLog.debug("FB: Adding logger [" + logger.getName() + "].");
		if (loggers == null) {
			loggers = new Vector();
		}
		loggers.addElement(logger);
	}

	/**
	 * No options to activate.
	 */
	public void activateOptions() {
	}

	/**
	 * Prints the message and the stack trace of the exception on
	 * <code>System.err</code>.
	 */
	public void error(String message, Exception e, int errorCode) {
		error(message, e, errorCode, null);
	}

	/**
	 * Prints the message and the stack trace of the exception on
	 * <code>System.err</code>.
	 */
	public void error(String message, Exception e, int errorCode,
			LoggingEvent event) {
		LogLog.debug("FB: The following error reported: " + message, e);
		LogLog.debug("FB: INITIATING FALLBACK PROCEDURE.");
		if (loggers != null) {
			for (int i = 0; i < loggers.size(); i++) {
				Logger l = (Logger) loggers.elementAt(i);
				LogLog.debug("FB: Searching for [" + primary.getName()
						+ "] in logger [" + l.getName() + "].");
				LogLog.debug("FB: Replacing [" + primary.getName() + "] by ["
						+ backup.getName() + "] in logger [" + l.getName()
						+ "].");
				l.removeAppender(primary);
				LogLog.debug("FB: Adding appender [" + backup.getName()
						+ "] to logger " + l.getName());
				l.addAppender(backup);
			}
		}
	}

	/**
	 * Print a the error message passed as parameter on <code>System.err</code>.
	 */
	public void error(String message) {
		// if(firstTime) {
		// LogLog.error(message);
		// firstTime = false;
		// }
	}

	/**
	 * The appender to which this error handler is attached.
	 */
	public void setAppender(Appender primary) {
		LogLog.debug("FB: Setting primary appender to [" + primary.getName()
				+ "].");
		this.primary = primary;
	}

	/**
	 * Set the backup appender.
	 */
	public void setBackupAppender(Appender backup) {
		LogLog.debug("FB: Setting backup appender to [" + backup.getName()
				+ "].");
		this.backup = backup;
	}

}
